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Head angle effect on top effective top tube length(4 posts)

Head angle effect on top effective top tube lengthcogmaster
Oct 26, 2002 6:31 AM
I am going to a frame that has a 73.5 vs 74.0 head angle. Given the same length top tube, what effect does the .5 degree slacker head angle have on the effective length of the top tube. Specifically, this would set stem back and bar back slightly. What would be the estimated effect on mm on a 58cm TT. Is it even significant enough to warrant going to a longer stem?

Thanks.
totally insignificant....C-40
Oct 26, 2002 6:46 AM
The difference would be 2mm or less. Since stems are made in 5mm minimum increments, don't worry about it.

Any difference in seat tube angle should be taken into account. A steeper STA increases the TT length by an average of 1.2cm per degree.
May be significant on handlingKerry
Oct 26, 2002 10:37 AM
It will be minimal on moving your bars relative to your saddle position. Depending on fork offset, it could influence your trail and therefore handling. It's pretty hard to find an "all else constant" comparison, but I would be more interested in possible changes in handling than in stem length.
re: Head angle effect on top effective top tube lengthblehargh
Oct 26, 2002 8:17 PM
assuming you've got about 10 cm between the top tube and your stem.

10 (cos 73.5 - cos 74) = .084 cm

pretty minimal. and i think i'm being liberal with the 10 cm allowance.

-d